Meeting Abstract

S1-1.9  Jan. 4  Feeding is a drag: cautious cirripedes curtail cirral casting when waves wash wildly MILLER, L P; Hopkins Marine Station, Stanford University

Size and form of filter feeding appendages have direct consequences for the efficiency of particle capture and the drag resulting from flow around the appendages. Barnacles are able to plastically alter the morphology of their cirral net between moults in response to the flow environment in which they live, but there appears to be a limit to the extent of alteration. As a result, in the most wave-exposed environments, high water velocities would be potentially damaging to barnacles, were it not for the benefits of behavior. To ascertain whether behavior allows barnacles avoid the consequences of drag, observations of barnacle feeding behavior on a wave swept shore were made using a video monitoring system. Barnacles react quickly, withdrawing their legs into the shell as large waves wash over them, and resuming feeding as soon as the flow slows. As larger waves and faster flows impact the site, barnacles withdraw more often. At flow speeds exceeding 4-5 m/s, barnacles withdraw for nearly every wave. By virtue of this behavioral trait, barnacles may in fact tune their cirral morphology to a measure of the environment more akin to the average or mode of the water velocities at a site, rather than to the extreme velocities that are more commonly measured and correlated with leg morphology